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Electricity from wood? An old technology with a new twist.

Ask Mother Nature and she'll tell you: living off the power grid is not a bad thing. As a rule, off-gridders will build smaller, greener, and more efficient houses than their grid-tied counterparts, and will be far more likely to practice conservation while treating their small pieces of paradise with due reverence. But this doesn't mean that everyone who lives off grid is cut from the same cloth.

Far from it.

Nothing brings out a person's individuality more than the way he or she goes about living with homespun power. For some, massive solar arrays, multiple inverters, and sleek, auto-starting propane generators tucked away out of sight in weatherproof enclosures are employed at great expense to help ensure that home power production is as seamless and worry-free as ... well, being hooked into the grid. For others, those who struggle daily with ill-conceived, piecemeal setups, the finer points of home power production will forever remain as mysterious as the U.S. tax code.

Then there are guys like Dan Bartmann, for whom the real point of making energy is to have fun making energy. The fact that the energy Dan produces with his curious apparatuses provides the power he needs to run his shop and the home he shares with his wife Michelle and daughter

Maya seems almost secondary. Because if it weren't fun--which is to say, instructive and awe-inspiring--he'd probably live like the rest of us left-brained off-gridders.

Wind power is Dan's stock-in-trade. As co-founder and co-owner of, a company he operates with a small-but-dedicated cadre of likeminded mountain-dwellers, Dan spends his time building and perfecting "homebrew" axial-flux wind turbines, while teaching other renewable energy enthusiasts how to do the same.

So what, I wondered, was he doing with a pre-WWI-vintage steam engine? Satisfying his curiosity? Harvesting energy to charge his battery bank? Yes and yes, and, as usual, having a great time doing it.


The power plant in question is a six-horsepower C&BC steam engine, manufactured in 1903. Dan found it at auction for less than $150 and stashed it away to let the possibilities simmer while he located a boiler capable of producing steam of sufficient volume and pressure to run the engine. A year later he acquired a four-horsepower vertical fire-tube boiler, manufactured in 1940 by the Lookout Boiler and Manufacturing Company, and set it up outside his shop next to the steam engine.

A pressure test with water and compressed air confirmed the boiler's integrity and another series of tests showed the C&BC was good to go. For the sake of life and limb--boilers and steam engines are not toys--Dan had the system checked out by a certified steam engineer before firing it up for the first time.

By itself, of course, a steam engine is nothing more elegant or useful than a spinning shaft. By anyone's reckoning it's a long way from lighting your house. For that, Dan needed an alternator that could turn the raw power of the C&BC into usable electricity. Big enough to be effective, but not so big as to put an unacceptable drag on his 100-year-old heirloom. Being in the alternator business, this was hardly a problem--Dan quickly fashioned a small axial-flux alternator and attached it to the C&BC's shaft. As it was designed to do, the alternator put out a steady 1,000 watts of power--equivalent to the energy output of about $5,000 worth of solar panels at noon on a sunny day--and it was immediately obvious that the engine was eager to do more.


The second (and current) alternator is similar to those he builds for his 17-foot wind turbines. It can easily churn out 2,000 sustained watts, delivered as three-phase alternating current (AC), and it is capable of more. Just how much more, Dan quickly discovered, was determined by the boiler's capacity: 2,500 watts was doable so long as someone was there to dutifully stuff wood into the firebox, but 3,000 watts was asking too much. Still, 2,500 watts was gratifyingly more than Dan had hoped for.

The amperage supplied by the alternator is routed through a trio of rectifiers, where it is converted from AC into DC (direct current) and sent at 48 volts to a 700-amp-hour forklift battery. There it mingles with the stored daily output from a 600-watt solar array and a 20-foot-diameter wind turbine on a 70-foot tower. (And, occasionally, with energy provided by Dan's two-kilowatt, hand-crank, Lister-type diesel generator, which turns its own custom axial-flux alternator at a leisurely 650 RPM.)

Because a steam engine uses a piston to produce rotary motion, it's easy to imagine that it works something like an internal combustion engine (ICE) that runs on pressurized water vapor instead of volatile, energy-dense fuel. But this is misleading. Unlike an ICE, the combustion that produces the power to run a steam engine occurs in the boiler's firebox, not the engine's cylinder. For this reason, steam engines are considered to be external combustion engines.

Inside the boiler, hot gases from burning wood (or coal, or twigs, or anything else that ignites) escape through the boiler's fire tubes, transferring heat to the volume of water that surrounds them. As the water boils, pressure is created inside the boiler and allowed to build to 80 pounds per square inch before steam is introduced into the steam engine's cylinder via a simple-but-effective sliding valve system.

Simple steam engines lack the complex system of valves, springs, pushrods and rocker arms found in modern ICEs. In their place a control rod, driven by an eccentric on the crankshaft, pushes and pulls a slide valve that alternately covers and uncovers ports through which high-pressure steam enters and leaves the cylinder. In Dan's C&BC engine, steam acts on both sides of the piston. As the slide valve opens the port to let fresh steam enter below the piston, it also opens the port that lets spent steam from the previous cycle escape through the top of the cylinder. Because the piston is alternately pushed by steam in either direction, it is called a double-acting steam engine. Unlike an ICE, the piston produces no compression beyond that which is supplied by the steam, since the intake and exhaust ports are opened simultaneously.


Are steam engines efficient? By the standard measure of such things, they have trouble stacking up to an ICE. Because of the number of phase transitions that must take place between combustion and power delivery (wood to fire, fire to hot water, hot water to steam, steam to rotary motion) Dan's simple steam engine could never be as efficient as his diesel generator. As Dan himself has figured, the best he can hope for is between five and 10 percent efficiency of converting wood or coal energy into usable electricity. By contrast, at eight kilowatt hours per gallon of diesel fuel, Dan's diesel generator turns diesel fuel into electricity with around 20 percent efficiency.


But that's only part of the story, and the misleading part, at that, considering that all Dan has to do to fire up his C&BC is to amble behind his house and cut down a dead tree. To run his diesel generator, on the other hand, he has to drive 36 miles into town to buy a can of fuel. The fuel did not originate in town, however. It was instead pumped from more than a mile below ground and shipped in a floating steel behemoth across an ocean or two, where it was offloaded at a refinery. There it endured the processes of distillation, catalytic cracking and hydro-treating--before being trucked in by a fuel-guzzling 18-wheeler to the filling station. If there's anything efficient about that, I'm missing it.

And here is a final irony. Whether it's powered by coal, or natural gas, or nuclear fuel, the power plant that produces the electricity needed to light up the glitzy filling station and pump diesel fuel into Dan's can (or your car) employs an electrical generator that's turned by a giant high-speed turbine.

A turbine driven by steam.

To see Dan's steam engine in action, visit It's a classical gas.



Rex Ewing is the author of several renewable energy books, including Power With Nature, Got Sun? Go Solar, and the newly released Crafting Log Homes Solar Style. He lives with his wife, La Vonne, in a handcrafted log home powered solely by the sun and wind in the foothills of Colorado. His books can be purchased at the Countryside Bookstore or at
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Author:Ewing, Rex
Publication:Countryside & Small Stock Journal
Geographic Code:1USA
Date:Nov 1, 2008
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